Fuel cells within which oxygen and hydrogen gas are used to produce electrical current are well known to the art. Typically, these fuel cells are comprised of a plurality of individual fuel cells each individual fuel cell including an anode chamber having a porous anode, and a cathode chamber having a hydrophobic porous cathode separated by an electrolyte "plate" (this may be an acid, an alkali or a solid polymer, electrolytic membrane) contained within a fuel cell housing.
As an example, electricity is generated in an acid fuel cell by the disassociation of hydrogen within the anode located on the surface of the electrolyte plate to form hydrogen ions and free electrons. The ions pass through the electrolyte plate to the cathode located on the opposite surface of the electrolyte plate, and the free electrons pass via suitable means to one terminal of the fuel cell. The cathode is similarly connected to the other terminal of the fuel cell from which free electrons are supplied and used to reduce oxygen gas. An additional and important by-product of fuel cells using solid polymer electrolyte membrane is that they produce liquid water on the surface of the cathode.
The formation of water at the cathode in such cells is undesirable as the liquid water tends to form a film which blocks further contact of oxygen passing through the cathode chamber with the surface of the cathode and reacting with the migrating hydrogen ions, which acts to decrease the electrical power production of the fuel cell. To alleviate this difficulty several methods have been developed to remove the water formed at this cathode surface. One method is to ensure a high flow rate of oxygen gas which, by virtue of the flow rate, acts to remove water on the surface of the cathode and to remove any entrained water within the cathode chamber. A second method of removing water is by use of a wick of fibrous material placed against the cathode surface. This wick, which is typically in the form of a flat braid, collects the water droplets formed on the surface of the cathode, and by virtue of capillary action of the fibers, draws off the liquid water formed in an individual fuel cell to a separate water reclamation chamber or system. Such a chamber or system may be situated at one end of the fuel cell or outside the fuel cell itself. In a third method disclosed in commonly assigned U.S. Pat. No. 4,543,303, (the contents of which are incorporated herein by reference) a novel fuel cell structure including an assembly for the withdrawal of liquid water formed in solid polymer electrolyte hydrogen/oxygen fuel cells is disclosed. There, a manifold assembly which includes a wettable porous valve metal is described. There, the individual fuel cells are oriented in a vertical orientation and connected to a common fluid exhaust manifold which includes an assembly to separate liquid water from the fuel oxygen gas. Therein, water formed at the cathode flows down the surface of the cathode due to gravitational forces and is separated within the manifold by the wettable porous valve metal. Although this is an improvement over the two prior disclosed methods used to withdraw liquid water from individual fuel cells, there remains a continuing need in the art for further devices useful for effectively removing liquid water formed in individual fuel cells.